Liquid level responsive device



June 16, 1942.. B, P, POND LIQUID LEVEL RESPONSIVE DEVICE Filed Feb. 25, 1939 2 Sheets-Shea?l l June 16, 1942. B, P, POND 2,286,929

LIQUID LEVEL RESPONSIVE DEVICE Filed Feb. 25, 19:59 2 sheets-sheet 2 |53; Mo |39 |25 lz., |20 39 HIGH PRESSURE |26 l/ |22 |45 cuT om |28 f ws SIZ? wz y l 64 |o l'soS E I-igfk man wz PRESSURE k CUT OUT TIMED FEEDER.

SIGNAL ,'mnntor F13' 5 Berrdm P. Pond.

s Wwf/M attorney Patented June 1.6, 1942 UNITED .STATES PATENT d OFFICE I. A 2,256,929 I LIQUID LEVEL RESPONSIVE DEVICE Bertram P. Pond, Minneapolis, Minn., assigner to Minneapolis-Honeywell Regulator Company, .Mlnneapolia Minn., a corporation of Delaware l Application February 25; i939, Serial No. 258,555

(Cl. 20G-122) 10 Claims.

carried away rapidly to maintain a compara-Y When the liquidv tively low tube temperature. level drops below that of the tube the heat cannot be carried-away so rapidly and the temperature of the tube rises. The resultant expansion operates a signal or a control of some sort.

A further object of the invention is to compensate the thermal element for variations in the temperature of the liquid or gas with which it is in contact so that the control will be eiected in response to liquid level alone.

A further object is to operate the control through a relay which is controlled by a snap switch operated by the thermal element and tc provide the snap switch with a resiliently mounted holding contact so as to eliminate the hazard of relay chatter'when the switch is just about ready to snap and the contact pressure is sub Y and snap switch in series with the heater for Vthe thermal element and to provide a balancing Figure 2 is a side view, partly in section, of my liquid level responsive device,

Figure 3 is a view, partly in section, showing a slight modification of the structure shown in Figure 2,

Figure 4 shows the schematic wiring diagram used where a manual reset is desired,

Figure 5 shows the schematic wiring diagram used'with the automatic return, and

Figure 6 shows a perspective view of the lever for actuating the snap switch.

Referring first-to Figure 2, the reference numeral li indicates a portion of the side wall of a container which houses a liquid Whose level may fall below and rise above a predetermined level. At this predetermined level in the wall il a tapped hole i2 is cut for the purpose of receiving a mounting member generally indicated at i3. This member may be made of any suitable material andis provided with a narrow portion Il, a wider screw threaded portion l5, and a head Ii of hexagonal form so that it may be rotated by means of a wrench. The mounting member I3 is screwed into the hole l2 by means of the threads l5 and then tightened. Located within the mounting member I3 is a supporting Y member of nonexpansible material generally inresistance to'be thrown in series with the heater Y when the snap switch is open so that the current flow through the heater will be maintained at 'a value at least sumcient to .hold the switc'li in its operated position.

A still further object of the invention is to mount the device in a container outside of the boiler and connected thereto in the manner of a gauge glass.

Another object is to make the rod of the rodV and tube thermostat of hollow form so that the heater used may be of the usual cartridge type. In this case holes may be cut in the rod so that the heat from the heater may be radiated directly to the temperature sensitive tube.

Still another object of the invention is to wire the control so that a signal, a heater for the boiler, or a feed water control, or any combination of these may be operated by the device.

These and other objects will become readily apparent to those skilled in the art as the iollowing specication is read in the light, o! the accompanying drawings, in which Figure 1 is a general view showing the manner in which the device of my invention may be mounted on a boiler,

dicated at Il. and which has a narrow portion I8 which nts snugly within the narrow portion of the mounting member and a wider portion I9 within the 'head i6 ofthe mounting member. The supporting member I1 is provided with a circumferential groove 20 in which is placed a suitable snap ring 2l. The supporting member Il is' slid longitudinally within the mounting member i3 until the ring 2| abuts the shoulder 22 within the head of the mounting member and the packing material 23 is then tightened by means of the packing nut 24 which has a screw thread engagement with the inside of the head I6. The end of the-supporting member i1 is provided with screw threads 25 on which screws a hexagonal nut 28 which may also be made of va nonexpansible material. A base plate 21 is provided with a hexagonal hole 2l by means of which it is placed over the nut 26 until it registers with a g'roove 29 in the nut 2S and the two are securely held together by rotating the plate 21 through an angle of 30. A locking plate 3l is then placed over the nut 26 and then a second supporting plate Il which registers with a second groove 32 in the nut 26 is rotated through an'angle of 30 to tix it with relation to the nut in the same manner as the plate 21. The plate. is provided with a slot Il in which and as the rod 58 moves toward the left the lever is mounted a spacer and a screw I5, the screw passing also through holes in the locking plate 8| and the plate 21.to`lock the entire structure together'and prevent their rotation with respect to the nut 28. The locking plate 88 has a hex- 5 agonal hole which exactly ilts the nut 28 and hence it is impossible to rotate this plate with respect to the nut.

'Ihe plate 8| is provided with ears 88 to which i is attached by means of screws 81 a switch panel 88. 'Ihe panel 88 supports a snap switch ci the over-center type, o'ne element of which is indicated at 38 and supported by means oi the screws 48.

The supportinmpme' 21 is provided with neri-'1e zontally and vertically extending portions 48 on tending portion 4I of the plate 21 by means ci screw 42.

Inserted within the other end oi the supporting member I1 and` seating against the internal shoulder 41 thereof is a tube 48 of suitable expansible material.l l'.'his tube is closed at its other end by means oi a threaded cap 49 'in which one end of a relatively non-expansible rod 58 is adjustably positioned and sealed. Slidably mounted over the rod 58 is a bobbin 5I oi insulating material about which is wound a coil of re'- sistance wire 52 to form an electrical heater for heating the tube 48. The heater 52 is provided with a pair oi' lead wires 58 and 54 which are protected by means oi insulating beads 55 through which the wires extend. The opposite end of the rod 58 is screw threaded into one end of a force transmitting element 51 of a relatively expansible material and the opposite end of this element is. in turn screw-threaded to another -force transmitting element 58 oi relatively nonexpansibie material.

As shown more clearly in Figure 6, a lever 88 is provided for operating the snap switch and a contacting element 8| having an insulated tlp 58 is adjustably-secured in the free end of the lever for making contact with the switch mechanism. 'I'he lower end 62 oi.' the lever 88 is turned in at an angle of 90 with respect to the rest of the lever and is adapted to carry a series of screws 83 and spacers 84 (Figure 2). Mounted on the spacers 8 4 is a ilrst ilexible reed 85, a spacing washer 88, a second U-shaped flexible reed 81, a second spacing washer 88, and a-lock plate 88 vwhich has screw-threaded engagement with the screws 88 which lock the above mentioned parts in assembled relation.

The nut 28 is provided with a pair of ears, one of which is shown at 12 in Figure 2, to which 60 the two legs oi the U-shaped re'ed 81 are fastened by means of screws 18. One end of the rod 58 is biiurcated as shown at 14and the reed 85 is inserted in the slot so formed and riveted thereto as shown at 15.

It will be seen that as the reed 85 is moved toward the right by rod 58 as shown in Figure 2, that the reed 81 will be caused toilex permitting rotation oi the lever 88 in a clockwise direction will be pulled in a counter-clockwise direction, this movement being permitted by the flexibility of the two reeds. e Attention is called to the fact` that the switch panel 88 is ymclunted independently oi the plate'75 the liquid within the container II.

noted that holes 18 in the inner end of the splash 'guard permit the tree circulation of liquid 21 forming the rear of the switch casing. Therefore the casing and relay panel may 'be bent and twisted withoutA changing the relationship bearound tube 48.

V' Inview oi the above description of the various parts, the operation of the device should now be clear. Electric current normally ilows through the heating element 52 causing itl to heat the tube 48 and when the liquid level is above that of the tube the vliquid will be in contact therewith and will dissipate the heat therefrom at a relatively -rapid rate which will maintain the temperature of the tube at a value which will be in the neighborhood of the temperature of the liquid. Under these conditions the tube will be in its relatively contracted position and the rod 58 will be moved toward the right where the lever will be out of contact with the switching mechanism. As the level of the liquid drops below the tube 48 it will expose the tube and the gas above the liquid will be unable to dissipate the heatfrom the tube at as rapid a rate as the liquid and therefore the temperature of the tube will increase causing it to expand. This expansion will pull the rod 58 toward the left rocking the lever 88 in a counter-clockwise direction and causing it to actuate the switching mechanism.

It will'be seen that as the tube 48 is in contact with the liquid within the container II that its Atemperature will vary as the temperatureoi the liquid which would normally aiiect `the operation of the switching mechanism. This is an undesirable function and for this reason means have been provided in this device for compensating the tube 48 for variations in temperature surrounding the device. This temperature compensation is accomplished by the member 51 which is of relatively expansible material and it i is located withinl the supporting member I1 which is composedof relatively non-expansible material. Therefore as the temperature of the liquid increases the tube 48 will be caused to expand, but this increase in temperature will be conveyed to the member 51 whichl in turn will expand relatively to the supporting member I1.

`The expansion of the tube 48 will cause a movement of the rod 58 toward the'left and the expansion of the member 51 will cause a movement of the rod 58 toward the right and the material and size of Vmember 51 have been so chosen that on variations in ambient temperature the expan-l 70. ing the tube. The beads 55 and the grooves 58 in member 58 tend to prevent the' conduction oi heat from the heater 52 and rod 58 to the expansible Ymember 51. Splash guard. 18 also serves to aid in the dissipation of any heat which may be conducted from tube 48 to members I1 and I4.

Figure 3 discloses a'slight modiilcation in the Figure 2. The tube 48 remains substantially the same but in this case the rodv is itself in the form of a tubular element as indicated generally at 85. The element 85 is loriginally in the form of a sheet which is welded together in three separate pieces. The first piece 88 is of a relatively nonexpansible material such as, invar, and the second piece is oi a relatively expansible material such as a chronium nickel alloy, and the third piece 88 is again of a relatively non-expansible material such as invar. This sheet is then rolled into the form of a tube and this tube is inserted within the tube 48 and connected' thereto. Cap 89 seals the open ends lof the tubes as shown at 90. c

The main advantage of this "construction is that the usual cartridge type of electric heater 9| may be inserted within the tube 85 in order to heat the tube 48.A In order to provide for the heat from the heater 9| being radiated to the stationary support |22 by means o! knife edges.

Indicated at |23 is an adjustably mounted statime it will be separated from the contact |23.

As thel lever 80 presses down on the leaf spring 39 the spring |20 will be carried over-center with respect to the support |22 and the toggle |2| will be snapped into engagement with anY adjustable stop |21. At this time the force exerted by the tube 48, the part 88 of the tube 85 is provided with a series of holes 92. The end ofthe portion 88 has a pair of inwardly extending ears'` 93 to which the reed 85 is riveted as shown at 94. The device is otherwise the same as shown in Figure 2. It will be clear that the expanslble material 81 compensates tubes 48 for variations in ambient temperatures in the same manner -in which the member 51 does.

In Figure l there is shown one Way in which this device may be mounted on a boiler |00. The boiler is provided with a pair of pipes and |02 which are connected above and below the normal water line in the same manner as the connections for a gauge glass. A container ||0 is supported from these pipes and connected to the interior oi' the boiler by means of pipes |83 and |04. This container is provided with a sump |05 and a blow-off lvalve |06. Connected hori-V zontally into one end of the container ||0 is my the container ||0 as shown at |01 and electrical conduits |08 andv |09 provide for the proper wiring.

It is pointed out that this device may be mounted in some other position than horizontal. The response will not be as critical as in the horizontal mounting but will give a response proportional to the liquid level. The switch may then be adjusted to be actuated at various, diierent liquid levels along the length of tube 48.'

, The liquid level responsive device of the presentinvention may be used to operate a signal whenthe liquid level falls below a predetermined point or if it is applied to a boiler it may act to shut oii theheat supplying means for the boiler,

f or if desired it may be made to control a device i'or`reestablishing the liquid level. Where it is applied to a boiler and operates to cut on the spring |20 tending to -hold the toggle |2| in engagement with the stop |21. Vis too great to be overcome by the resilience of the blade 39 so that the switchwill remain in this position even though .the lever 60 is withdrawn from engagement with the leaf spring 39. A manual reset button |28 has been provided for manually engazing the leaf spring 39 to return this switch to its closed position.

' Indicated at |30 is a relay winding which controls the positions of the switch arms |3|, |32, and |33. The'anns |3| and |33 cooperate'with in contacts |34 and |35 and the arm |32 cooperates with the out contact |38.A In series with the switch arm |32 is some form of signalform of a space thermostat, or a boiler thermostat, or any other type of controlling device. The element |38 is adapted to move a switch arm |38 into and out of engagement with the stationary contact |40. 'In series with the element |38 is a.

' safety device |4| such as a high pressure cut-out and a motor |42 which controls the supply of heat to the boiler.

When the level of the liquid in the boiler is above that of the liquid level responsive device I0 and the tube 48 will be relatively cool and in its contracted position, at which time the lever will be withdrawn from engagement with the leaf spring 39 and the switch contacts will be closed.

At this time the relay |30 and the heater 52 will heat supply to the boiler when the water level within the Aboiler drops below a predetermined value, it will probably be desired that the switch operated by the liquid level responsive device be of the non-return type requiring a manual reset.

A control circuit for such a system has been diagrammatically illustrated in Figure 4.

The liquid level responsive device has been diagrammatically illustrated at |0 `as has the switch actuating lever and the leaf spring 39 against which the lever 50 bears. The leaf spring 39 is contact carrying toggle |2| 'whichengages the |45, conductors |46 and |41, relay winding |30, conductor |48, stationary contact |23, contact |24, contact arm |2|, |22, conductor |49, heater 52, and conductors |50 and |5| back to the other line wire |52. The energization of the relay-|30 causes the closure of the switch arm |3| and its contact |34 which sets up a. holding circuit for the relay |30 through the holding contact |24 independently of the stationary contact |23. This holding circuit is as follows: conductor |41, relay Ywinding |30, conductor |53, switch arm |3|, contact |34, conductor |54, resilient arm |25, contact |24, Vand toggle arm |2|. The reason for this holding circuit is that when the tube 48 responds to low water and causes the lever 50 to engage the leaf spring39 there will be a point where the switch is just about ready to snap and the pressure between-the contacts |23 and |24 will be practically zero. At this time in the absence of the holding circuit a slight vibration would cause these contacts to chatter which would result in their burning and also causerthem to produce an undesirable intermittent operation of the relay |30. With the holding contact |24 the clr'cuit through the relay will remain established through the contacts ,|24 and the toggle arm |2| and this circuit will not be broken until after the to engage stationary contact series with the motor |42. At this time, assum- Energization of the relay |30 causes arm |33 |35 which is in ing that the high pressure cut-out |4| is closed, the motor |42 is under the command of the condition responsive device |38 so that each time there is a demand for heat the following circuit is closed through the motor |42; line wire |45, conductor |60, contact |35, switch arm |33, conductor |6|, high pressure cut-out |4i, conductor |62, contact |40, switcharm |39, condition responsive element |38, conductor |63, motor |42,

and conductor |54 back to the otherv supply line Under normal c nditions therefore the condition responsive de 'ce will energize Aand deenerygize the motor 42 in accordance with the vdemand for heat. In the event that the water level in the boiler 'becomes too low and exposes the tube 48, it will expand and cause the lever 60 to snap the switch to open position. This-deenergizes the relay winding |30 causing the switch arms |3| and |33 to disengage contacts |34 and |35, respectively, and the switch arm |32 to engage the stationary contact |36. The dropping out of switch arm |33. breaks the circuit to the motor |42 making it impossible to supply heat to the boiler and as arm |32 engages contact |36 the following circuit is established to the signalling device |31: line wire |45, conductors |46 and |65,'

contact |36, switch arm |32, conductor |66, signalling device |31 and' conductors |61 and|5| back 4tothe other supply line |52. 'I'his circuit energizes the signal and calls attention to the fact that the Water in the boiler is low and the heating device has been shut down. It will be noted also that4 the' circuit to the heater 52 for which on low water will not only cut-oir the supply of heat to the boiler but will energize a feeder to introduce' water to the boiler to restore the water to the normal level In such a system it is desirable that the switch 'actuated by the liquid level responsive device be of the automatic return type sov that it will reclose and put the system into normal operating condition after the water level has been restored. Therefore the stop |13 is provided to limit the movement of the toggle arm vl2| in switch opening direction and in this position the spring |20 may b e-overcome by the leaf spring 33 when the lever 6l is withdrawn therefrom so thatthe force exerted by spring 33 will carry spring |23 back over-centerwith respect to support |22 and reclose the switch |2'|,'|,24,and|23. I

to b e responsive to the increase inliquid level the heater` 52 must remain energized while the toggle switch |2| is in open position. In order to provide for this a third switch arm |1| is provided for actuation by the relay |30. This switch arm cooperates with an out contact |12'. On low level the tube 48 expands and opens the toggle switch |2| deenergizing the relay coil |30causing the switch arm |1| to engage contact |12. This causes a circuit to be closed from the supply conductor |45 through yconductors |46, |13, contact |12, switch arm |1|, conductor |14, balansing resistance |15, conductor |16, conductor |49, heater 52 and conductors |50 and |5| back to the other side of the supply line |52. The balancing resistance |15 is chosen so'asl to have a A value which will provide for a flow of current through the heater 52 which is at least suflicient to maintain the tube 43 expanded sumciently to keep toggle |2| in engagement with the stop |10 while the liquid level remains below the tube 48.

In series with the signal circuitr is a feeder |18` which controls the flow of water in the boiler and as set forth above, this circuit is energized through the switch arm |32 and the out contact |36 when the relay coil |30 is deenergized `on low water. X

As the water level rises due to the enerigization of the feeder |13 it will againsurround the tube. causingit to dissipate its heat and contract thereby withdrawing' the-lever 60 from the will place the motor |42 again under the'control v of the condition responsive element |36 ,and the system will again bein normal running condition.

In order that the liquid level be normally a few inches above'the level of ther-tube 48 a time delay mechanism may be introduced in combl nation with the feeder |18 so that it will run a predetermined length of time after the opening of the control circuit at |32, |36.

It will be appreciated of course that this system need not be used with all three controls but may be used with any one or any combination of them. It is obvious that this device could also be used to operate any other control anyone might desire to be actuated in accordance with liquid level. Also the device may be used as a liquidlevel controller independently-of the boiler, that is. it may be inserted into any liquid container and through the feeder |18 control the liquid level.

Various changes and modifications of this invention may occur to those who are skilled -in the art and I therefore Wish it to be understood that I am to be limited` only byv the scope of the f appended claims and not by the specific embodiments disclosed.

I claim as my invention: f

1. Liquid level responsive means comprising a temperature responsive device mounted 'so as to have relatively good thermal 'conductivity between itself and a liquid when said liquid is at orabove s predetermined level and relatively poor thermal conductivity between itself and said Suquld when-said liquid is bemw said predeter- W --m-orderforihe nqum revel responsive device mined level'. means delivering a temperature changingmedium 'to said devicev whereby its temperature is. maintained at a value other than.

that of the liquid and varies as said liquid level rises above and falls below said predetermined level, and means compensating said device for mitting element.

variations` in the temperature of said liquid to cause said device to function responsively substantially to liquid level only.

2. In a liquid level responsive means, in combination, atemperature responsivedevice comprising a metal of relatively high thermal expansion and a metal of relatively low thermal l expansion, means mounting said device so as to have relatively good thermalV conductivity between itself and a liquid when said liquid is at for above a predetermined level and relatively poor thermal conductivity between itself and said liquid when said liquid is below said predetermined level, means delivering a temperature changing medium to said device whereby its temperature is maintained at a value other than that of the liquid and varies as saidliquid level rises above and falls below saidpredetermined level,

bination, a temperature responsive device comprising a tube of expansible material, means supporting one end or said tube, a torce transmitting member of relatively non-expansible material connected to the other end of said tube, means mounting said device so as to have relatively good thermal conductivity between itself and a liquid when said liquid is at or above a predetermined level and relatively poor thermal conductivity between itself and said liquid when said liquid is below said predetermined level. means delivering a temperature changing mecontrol means is moved responsively to the level of said liquid only.

6. In combination, a container, liquid in said container, an expansible tube, means mounting said tube withinvsaid container at a predetermined level, a force transmitting elemento! relative non-expansible material connected to the inner end oi' said tube and extending longitudinally inside of said tube, an electric heatingelement mounted within said .tube and radiating heat thereto, control means actuated by said force transmitting element, and a. member of relatively expansible material between said force transmitting element and said control means, said member expanding substantially the same amount as said tube on variations in ambient temperature whereby said control means is actuated independently of ambient temperature.

7. In combination, a container, liquid in said container, an expansible tube, means' mounting said tube'within said container at a predeter mined level, a force transmitting element of relative non-expansible material connected to the inner end of said tube and extending longitudinally inside of said tube, a member 'of relatively expansible material adapted to expand the same amount as saidV tube on variations in ambient temperature, said element and said member being in tubular form and integrally joined at one end to make a continuous tube, an electric heater within said tube, and control means operated dium to said device whereby its temperature is i `maintained at a value other than that of the container, an expansible tube, means mounting said tube within said container at a predetermined level, a force transmitting element of relative non-expansible material connected to the inner end of said tube and extending longitudinally inside4 of said tube, said element having a hollow portion, an electric heater located within the hollow portion of said element, said element having holes in said hollow portion whereby heat may be radiated i'rom said heater to said tube, and control means operated by said force trans- 5. In combination, a containen'liquid in said container, an expansible tube, means mounting said tube within said container at a predetermined level, a'force transmitting element of relative non-expansible material connected to the vtube and element for compensating them for changes in ambient temperature whereby said by said element and member.

8. In combination, a container, liquid in said container, an expansible tube, means mounting said tube within 'said container at a predetermined level, a force transmitting element of relative non-expansible material connected to the inner end of said tube and extending longitudinally inside of said tube. a member of relatively expansible material adapted to expand the same amount as said tubeon variations in ambient temperature, said element and said member being in tubular form and integrally joined at one end to make a continuous tube, an electric heater within said element, said element having holes therein to facilitate the radiation of heat from said heater lto said tube, and control means operated by said 'element and member.

9. .In a liquid level responsive device, in comblnation, a control member, an actuator operativev ly connected thereto, a temperature responsive first member having good thermal conductivity to the liquid when in contact therewith and poor thermal conductivity when not in contact there-` with, said iirst member beingv capable of impressing a force upon said actuator in'one direction upon a temperature increase, a temperature responsive second member capable oi' impressing a force upon said actuator in the opposite direction upon a temperature increase, and means deliverlng a temperature changing medium to both of said temperature responsive members, said members because of thermal conductivity to 'the liquid .being adapted to compensate each other for variations in liquid temperature whereby the resultant movementof said actuator is substantially dependent upon liquid level only.

10. Ambient temperature compensating means for a liquid. level control including a member having good thermal conductivity when in contact with the liquid and poor thermal conductivity when not in contact therewith comprising, the 'combination of, force translating means, t normally heated temperature responsive rst means inthermal conductivity with the liquid capable of impressing a directio fasce npon said transv latins means fer a given temperature variation, 'and temperature responsive seeond means in thermal conductivity with the liquid capable of sates said mst member for ambient temperature y variations beceuseof thermal conductivity to the liquid and causes said translating means to have a. force impressed thereupon responsively subimpressing an oppositey directional force upon y 5 stantially to liquid level only.

said translating means for a given temperature variation. whereby said second member compen- BERTRAM P. POND. 

